Day-to-day variability of stress biomarkers during a music intervention in people living with dementia and their family caregivers.

Examination of the variability of stress biomarkers among people living with dementia and their family caregivers can provide evidence of stress reactions and corresponding self-regulation capacities, but no such research has been conducted to date. The aim of this study was to examine day-to-day variability patterns of salivary biomarkers in dyads of people living with dementia and their family caregivers and to investigate differences in variability patterns between music intervention and control groups. This study involved secondary analysis of data collected during a two-group, non-randomized open trial examining the effects of an 8-week music intervention on physiological stress markers. A total of 5791 salivary samples from 34 dyads were used to analyze the variability of morning and evening cortisol and of morning dehydroepiandrosterone sulfate (DHEA-S). The variability indices employed were the intra- and inter-individual standard deviation, coefficient of variation, and intra-class correlation coefficient. We found that family caregivers in the music intervention group had significantly greater coefficients of variation for all three biomarker endpoints than those in the control group. Our findings provide evidence that stress biomarkers in family caregivers with functional self-regulation capacities may be more likely to respond to music intervention. However, stress biomarkers in people living with dementia may not be responsive to music intervention, possibly due to their dysfunctional self-regulation capacities. Future stress biomarker studies involving dyads of people living with dementia and family caregivers should consider biomarker variability patterns in determining the effectiveness of behavioral interventions.